2009 Pontiac G8 GXP - Ferocious Four-Door

Some hobbyists argue that Pontiac performance died in '79 when the last 400 was factory installed into a Firebird. Others, like Bob Cook of Allen, Texas, are enjoying the last performance vehicles the Division offered before The General pulled the plug on the entire line in 2009.

If you've never experienced the creature comforts, suspension and handling refinements, and sheer rate of acceleration that late-model G8s provide, you're missing out on what Pontiac got right. A rare combination of good looks, stout performance, manageable fuel economy, and four doors, it's a vehicle that does everything well, and that includes hauling the family.

The 58-year-old aircraft-equipment machinist isn't a rookie when it comes to hard-running Pontiacs. "In 1972, my dad bought my step-mom a '73 Grand Am for Christmas and I was able to drive it occasionally. As a 17-year-old kid at the time, it was the cat's meow. It looked great and the 400 had plenty of punch. That set the type of car I wanted," he recalls.

A few years later, Bob was driving his '73 Buick Riviera when he passed a Pontiac dealership and spied two new limited-edition Can Ams being unloaded from the transporter. He immediately wheeled around, went in, and negotiated a deal for one of them on the spot.

"It was among the hottest cars available at the time. I had to have one," he says. "I found it was like owning a black-and-gold Trans Am. I absolutely loved the color combination and everybody wanted to know about it."

As Bob married and began raising a family, it became evident that the two-door coupe wasn't exactly the best fit for his growing needs. "I traded the Can Am in on an '82 Caprice. With our second child coming, I really had little choice," he laments. A move he always regretted, he was, however, able to purchase not one, but two Can Ams later in life, and a number of other Pontiacs over the years.

A Brazen Orange '06 GTO was Bob's latest foray into the Pontiac performance world during the mid-'00s, and as much as he loved it, it had a few distinct shortcomings.

"It ran very well, but I wanted a four-door so bad it hurt," he admits. "I needed a car with a trunk to put my golf bag in and with four doors so four of us could ride comfortably to the golf course. That just wasn't possible with the GTO."

4/11The G8 GXP was Pontiac’s last hot rod and it was arguably the fastest production Pontiac ever. Owner Bob Cook improved the performance of his White Hot ’09 model with supercharging. The 11-second four-door contains a mildly modified exterior, too.

Bob considered a G8 for his daily driver, but the 361hp 6.0L in the GT just didn't pack enough punch for him. A GXP would, however, fit the bill nicely. The sporty, four-door sedan was powered by an LS3 V-8 cranking out 415 hp at 6,000 rpm and 415 lb-ft at 4,600 rpm.

Backed by a six-speed transmission, whether automatic or manual, new-vehicle test drives at the time suggested the G8 GXP was the quickest production Pontiac ever produced. It regularly accelerated from 0 to 60 mph in less than 5 seconds and boasted quarter-mile times in the low-13-second range with trap speeds of 106-108 mph.

Bob and his neighbor share a common interest in fast cars, and both happened to be looking for a GXP at the same time. "I just couldn't resist it," say Bob. "We looked hard but found they sold as soon as we located them. He found a Pacific Slate-colored one with an automatic transmission for sale in Austin, and we made an agreement with Sewell Pontiac in Dallas to bring the car up for a preview. We assured them one of us would buy it."

Bob's neighbor had refinanced his house, and fortunately for Bob, the approval came through just as the GXP arrived at Sewell.

8/11The center console houses the 6L80E’s automatic shifter, which also allows for tap-shifts in Sport mode. In the center of the dash is a small gauge that displays the Super Chiller’s temperature.

"It temporarily froze his assets, so he wasn't able to get financing for it at that moment, and I was able to buy it. It was very fast, and rode and handled extremely well. I absolutely loved it, but about a year later I was laid off, and with six other vehicles in the garage, I couldn't really justify the payments. I sold it to him and he still owns it," Bob says.

Bob was redeployed in 2011 and immediately set out to find a replacement GXP. "The performance prompted me to get another. In October of that year, I ran across a White Hot G8 GXP on the Internet. It was a late-model trade-in on a dealer lot in Springfield, Illinois. It had 23,000 miles and looked very clean in the photos. I bought it for $32,000 without actually seeing it in person and was concerned that it wouldn't be as nice as it seemed. When it arrived, I found it was better than expected."

Bob immediately started using his newest GXP as a race car. "It was fairly quick in stock trim, but I wanted to prove you could get a four-door to run 11-seconds and still be a great, all-around car. I knew the kind of power easily capable with supercharged combinations, and it seemed to be the best bang-for-the-buck approach."

It seemed at the time that Magnuson was the only company producing a complete supercharger package for the G8. Bob notes: "It was recommended by several people and Mike White of Whiteside Customs in McKinney, Texas, was a Magnuson retailer. I bought the kit from him, and as I got more information about it, I decided to use his shop for the install. It was at that time that I actually started working for Mike part-time as an installer. I paid him to install the supercharger, and then he paid me to install it!"

9/11So cleanly installed, if you didn’t know better, you might first think that this Magnuson supercharger was factory installed. Bob performed the install while working at Whiteside Customs in McKinney, Texas. Whiteside’s Mike White painted the engine covers, which were supplied by Rotofab.

Starting with the stock LS3, Bob left the bottom end just as GM assembled it. The 6.2L mill features a 4.06-inch bore and 3.62-inch stroke, yielding 376 ci. The LS3's "821" cylinder heads produce a compression ratio of 10.7:1 and are capable of flowing more than 325 cfm on the intake side in stock form. The only modification was the addition of PRC 650 valvesprings to control the stepped-up valve action created by a custom hydraulic roller grind from Crane Cams, boasting 225/230 degrees of 0.050-inch duration and more than 0.600-inch valve lift with the stock 1.7:1-ratio rocker arms to take advantage of the available airflow.

10/11Beyond a custom-spec cam and matching valvesprings, the LS3 is largely unmodified. The intake tube included in the Magnuson kit connects to the stock airbox, which houses a reusable K&amp;N filter. The LS3’s 90mm throttle body has been treated to a black-wrinkle finish like that of the Magnuson blower. JHP Products supplied the Holden Products radiator cover.

The cylinder heads are topped by the aforementioned 2300-series Magnuson supercharger. A 3.8-inch pulley limits boost to about 5.5 psi with the final tune.

"The Magnuson intercooler is cooled by a Super Chiller unit from Active Interchiller in St. Petersburg, Florida," Bob explains. "It keeps the intercooler coolant close to freezing when activated to prevent any heat-related timing loss that can reduce performance when racing. A switch disables the heat exchange to prevent reheating the coolant that has been chilled."

To ensure that the LS3 didn't go hungry on the 93-octane pump gas it consumes, Magnuson supplied new 59-lb/hr fuel injectors in the kit, but the rest of the fuel system is stock. The 6L80E six-speed automatic transmission is plenty capable, but Bob added a 2,800-rpm-stall Vigilante torque converter from Precision Industries to launch a bit higher off the line. The original 3.27 gear set and limited-slip differential are housed in the GXP's independent rear suspension axle.

Getting the LS3 tuned was only slightly more complicated. Bob had Quality Motor Sports in Lewisville, Texas, provide him with an ECM core, which was programed with a base tune. That allowed him to drive the GXP to Quality's shop, where tuner Patrick Sparks expertly calibrated the ECM and TCM. The GXP was then treated to some mild suspension and appearance modifications, and was ready to hit the street and the strip.

11/11The rear wheelwells were rolled slightly to attain sufficient clearance for the beefy wheel-and-tire combo. The GXP’s braking system remains completely original, save for custom paint on the calipers. Tinted windows and a shark-fin antenna complete the exterior modifications.

Bob best explains the blown GXP's performance after tuning: "It has a lot of guts. You just hit the pedal and hang on. It makes a lot of noise in First and Second gear. Once the tires stop spinning, it really wakes up in Third gear and starts pulling hard. It accelerates as well as any other race car I've driven."

Despite a race weight of 4,270 pounds, it has blistered the pavement at Texas Motorplex where it turned the quarter-mile in 11.81 seconds at 120 mph.

Bob believes there's much more power in it and expects to unleash it with subsequent dyno-tuning sessions. And if that isn't enough, he's also considering a 3.4-inch-diameter pulley, which will increase the Magnuson's boost toward 7 to 8 psi.

One of Bob's favorite moments with his GXP occurred on the Hot Rod Power Tour during a stop in Memphis. "We were at a track day, and it was fully loaded with our luggage and equipment, and sitting on street tires. It was nearly 100 degrees and the humidity seemed nearly as bad. We lined up with a C6 Corvette and he saw nothing but taillights."

Bob doesn't use his GXP as daily transportation, and it now has approximately 50,000 miles on the odometer. "I take it often for pleasure runs or on short trips. It gets 16 to 17 mpg around town and about 22 mpg on the highway, but it's hard to keep your foot out of it."

Bob's charged GXP earned Gold In Class at the 2013 Pontiac Southern National event. And based on what he has in store for his four-door, you can rest assured you'll see it in the winner's circle whether it's on the show field or the dragstrip!